Nucleus
The Nucleus is the cell 'control centre' found in Eukaryotes. It is the source of the cell's DNA and RNA and is where Transcription takes place.
It is comprised of:
- A Nuclear envelope = twin membrane that protects contents from cytoplasm and macromolecules that could interfere with internal processes. Nuclear pores perforate the membrane and allow small molecules to diffuse freely in and out of the structure. Macromolecules (like nucleic acids) are moved into the nucleus via active transport.
- Nucleoplasm = this material comprises mostly of Chromatin
- Nucleolus = 'core' of Nucleus, relatively unstable structure without a membrane contains rRNA (ribosomal RNA) and is the site of Ribosome synthesis.
A nucleus is also the centre of an atom, comprised of protons and neutrons.